Fluid operated safety jack apparatus



March 27, 1951 H. E. NELlUS FLUID OPERATED SAFETY JACK APPARATUS I5 Sheets-Sheet 1 Filed Dec. 20, 1945 March 27, 1951 H, E, NEWS 2,546,904

FLUID OPERATED SAFETY JACK APPARATUS Filed Dec. 20, 1945 5 Sheets-Sheet 2 A 12 1 12-2 20 [2 65 62 awe/MM Harald EiNelz'us W- $52M fgl@ March 27, 1951 H, E, uus 2,546,904

FLUID OPERATED SAFETY JACK APPARATUS Patented Mar. 27, 1951 FLUID OPERATED SAFETY JACK APPARATUS Harold E. Nelius, Canton, Ohio, assignor to The Weber Dental Manufacturing Company, Canton, Ohio, a corporation of Ghio Application December 20, 1945, Serial No. 536,098

6 Claims.

The invention relates to fluid operated safety jack apparatus which is of general use and which is particularly adapted for use as the raising and lowering mechanism in a dental or surgical chair or the like.

In a fluid operated jack apparatus, the jack includes a piston and cylinder which are relatively reciprocable with respect to each other, the cylinder having a cylinder head opposite the piston, and the working fluid, usually oil, being pumped through an opening in the piston or in the cylinder or cylinder head into the cylinder 7 chamber formed by and between the piston and the cylinder and cylinder head.

When the cylinder and piston reach a desired position of relative extension with respect to each other, it is necessary that some form of stop means he provided to prevent further relative movement away from each other of the piston and cylinder head.

' sure unless properly relieved overloads the motor and may cause it to burn out or wreck the other parts of the jack apparatus. In most cases prior to the present improvements the pressure relief means for the cylinder chamber working fluid has included mechanism having a relatively large number of parts which have been associated with the fluid release or discharge'valve means which is always incorporated in a fluid operated jack to selectively provide for the removal of the working fluid from the cylinder chamber when it is desired to effect relative retraction of the piston and cylinder, that is, movement of the piston and cylinder head towards each other.

In a fluid operated jack apparatus used as a lift means in a dental chair, or the like, there are further requirements that the cylinder chamber fluid pressure relief means be smooth in operation and produce no perceptible alternate jerky drops and rises of the chair upon which the patient is seated, and also the pressure relief means should operate quietly as well as smoothly so as to produce no disturbing noises or vibrations,

If, as in many cases, mechanical abutment stop means are utilized, im-

2 The objects of the present invention include the provision of improved fluid operated safety jack apparatus of general use and having improved combined stop and pressure relief means operative to limit the maximum relative extension of the piston and cylinder and to prevent the building up of excess pressure in the cylinder chamber working fluid at maximum relative extension of the piston and cylinder, the combined stop and pressure relief means including no moving parts subject to breakdown by wear, and being entirely independent of the fluid release or discharge valve means.

Further objects of the present invention include the provision of such fluid operated safety jack apparatus particularly adapted for use in a dental or surgical chair or the like, and in which the combined stop and pressure relief means for the cylinder chamber working fluid operates without producing jerking relative movements of the piston and cylinder, perceptible vibrations, or noises.

Further objects of the present invention include the provision of such improved fluid operated safety jack apparatus, which is simplified in construction and in the arrangement and operation of its parts, so that the improved jack apparatus may be manufactured with facility and economy, and may be operated substantially in definitely without requiring maintenance of the improved safety relief means.

The foregoing and other objects are attained by the fluid operated safety jack apparatus, parts, improvements, combinations, and subcombinations, which comprise the present invention, and the nature of which is set forth in the following general statement, and preferred embodiments of which together with their mode of use are set forth in the following description, and which are particularly and distinctly pointed out and set forth in the appended claims forming part hereof.

The nature of the present invention may be stated in general terms as including in fluid operated jack apparatus, a piston and cylinder which are associated with each other for fluid sealed reciprocation with respect to each other, the cylinder having a cylinder head opposite the piston, and a cylinder chamber being formed by and between the piston and the cylinder and cylinder head, which may be otherwise termed cylinder chamber forming members.

One of the cylinder chamber forming members has an opening formed therein and pump means communicatingly connected with the opening provements hereof in the form of a dental chair' fluid operated jack apparatus are illustrated in the accompanying drawings forming part hereof, and in which Figure 1 is a vertical sectional view as on line II, Fig. 4, showing the improved fluid operated jack apparatus in the form of a motor driven fluid operated jack apparatus particularly adapted for use in a dental chair and the like, the vertical section passing through the vertical center of lift axis, and the cylinder and other vertically movable parts being shown in their retracted or down positions;

Fig. 2, a view similar to Fig. 1, showing the piston, cylinder, and certain other associated parts removed from the complete jack apparatus shown in Fig. 1;

Fig. 3, a view similar to Fig. 1, in which the cylinder and other vertically movable parts are shown in their fully extended or up positions;

Fig. 4, a top plan view with portions broken away and shown in section, looking in the direction of the arrows 4 -4, Fig. 1; and v .Fig. 5, a horizontal sectional view as on line Similar numerals refer to similar parts throughout the several views of the drawings.

The improved fluid operated safety jack apparatus is indicated generally by ID and has a center of lift axis indicated by the dot-dash line II which is vertical as shown.

The jack apparatus It includes a base member indicated generally by I2, a supporting member indicated generally by I3, and elevator or lift means indicated generally by I4 operatively interposed between the base member I2 and the supporting member I3 for extending and retracting the supporting member I3 with respect to the base member 52 in the direction of the center of lift axis II.

The lift means I4 includes an electric drive motor indicated generally by i5 and control means indicated generally by I8 for the motor I5 and other parts of the lift means.

The electric drive motor I5 is at one side of the center of lift axis II, and the control means I6 as shown is diametrically opposite the motor I5 on the other side of the center of lift axis II.

The base member [2, the supporting member I3, and the lift means I 4 are all preferably rotatable about the center of lift axis II, as by means of a base flange ring I9 which rests upon the floor as where the jack apparatus is located and which has an upper annular track 2| upon which roll lower wheels 22 journaled at the bottom of the base member I2.

The lower end of the base member I2 is externally cylindric and has a. lower bearing band portion I2i rotatably fitting an internally cylindric bearing band I 22 formed in the base flange ring I9.

Above the track ZI the lower end of the base 4 member I2 has formed therein an external groove I2-3, and a plurality of retaining tongues I2-4 are separably secured on the top of the track 2| to the base flange ring I9, each retaining tongue extending into the groove I2-3.

Releasable tongue and notch engaging means indicated generally by 23 (Fig. 4) are preferably interposed between the base member I2 and the base flange ring I9 for selectively engaging the base member I2 and the parts carried thereby at any of a plurality of selected positions after rotation thereof on the base flange ring I 9.

The base member I2 preferably as shown includes a larger inwardly flanged bottom ring 24 on which the rollers 22 are mounted and having the bearing band portion I2I and groove I23, a smaller top ring 25 spaced above the bottom ring 24, and strut walls 25 extending between and connecting the bottom ring 24 and the top ring 25, the sides of the strut walls 26 being circumferentially spaced from each other and forming openings 2'5 and 28 at opposite sides of the axis I I. separable skirt walls 29 depend downwardly and outwardly from an upper end connection with the top ring 25 and provide cover means for the bottom and to rings 24 and 25, the strut walls 25 and the various parts mounted on and car ried thereby.

Adjacent the opening 27, as shown at the left of the axis I I, an outwardly extending cantilever platform 30 is connected at its inner side to the base ring 24, and the motor 5 5 is mounted on the platform 33, and the skirt walls 29 have formed therein a bulge SI within which is located the platform 36, the motor I5, and adjacent parts.

The motor I5 is part of a motor pump'unit indicated generally by 32 which also includes a rotary fluid pump indicated generally by 33 drive connected with the motor shaft.

The control means I6 as shown includes a horizontal pedal lever shaft 34 extending on opposite sides of a radial plane including theaxis I I and supported on bracket means 35 mounted on and extending upwardly from the bottom'ring 24. A plurality of three pedal levers 36, 31, and 38are pivotally mounted or secured on the shaft 3 3 and extend outwardly therefrom through an opening 39 in the lower end of the skirt wall 29.

The improved fluid operated safety jack apparatus II] as shown is particularly for use as part of a dental chair in which usual dental chair superstructure, not shown, is secured upon the upper end of the supporting member I3.

The supporting member I3 as shown is a tubular member whose longitudinal axis coincides with the center of lift axis II and which has formed in its upper end a plurality of threaded sockets 48 for connection with the supported superstructure.

The supporting member I3 is telescoped within an intermediate tubular member M which is itself telescoped within the base member top ring 25 and strut walls 25 in the extended positions of the telescoping parts, and the intermediate tubular member 4| also telescopes within the base member bottom ring 25 in the retracted positions of the telescoping parts. 7

At each of diametrically opposite sides of' the center of lift axis II, the supporting member I 3 has a set of two longitudinally extending tracks each indicated by 42, each track having its longitudinal axis parallel with the axis II, and each track of each set being transversely at right angles with the other track. On the inside of the intermediate tubular member 4i opposite'each track 42 there is operatively mounted a set of upper and lower cylindric rollers 43, the rollers rolling on the opposed track.

Similarly, the intermediate member 4| has on its outside opposite sets of longitudinally extending tracks, each indicated generally by 44, each track of each set being transversely at right angles with the other, and on the inside of the base member top ring 25 and struts 26 opposite each track 44 there is mounted a set of upper and lower cylindric rollers 45, the rollers rolling on the opposed track.

The telescoping movements of the members l3, 4|, and |2 is thus effected by opposed and transversely angled track and roller guide means which provide for smooth and frictional telescopic movements and prevents relative rotation of the telescoping members.

Movement of the inner supporting member |3 in the direction of the axis of lift H, as shown, is effected by movement of the intermediate tubular member 4| by fluid pressure and by means of a pair of usual chain lift means each indicated generally by 46, interposed between the members l3, 4|, and I2.

Each chain lift means 4'5 includes a pulley 41 rotatably mounted on an upper inner face of the member 4| over which passes a chain 48. One lower end of each chain 48 is connected at 49 with the lower end of the member i3, and the other lower end of each chain 48 is connected in a usual manner with the upper end of a rod 48-| (shown in Figs. 1 and 3), the lower end of which is connected. with the lower end of the member l2.

The improved piston and cylinder lift means which are one of the particular improvements of the present invention are indicated generally by 5D, and are operatively interposed within and between the base member l2 and the intermediate member 4| for lifting the intermediate member 4!. The piston and cylinder lift means 53, as shown, includes a bridge member 5| which is dependently carried by the flange 52 of the base member bottom ring 24. A tubular piston rod 53 has its lower end secured to the bridge member 5|. The piston rod 53 is longitudinally coaxial with the center of lift axis H, and has an annular piston 54 on its upper end, the opening 55 of the annular piston 54 communicating with the upper end of the bore 55 of the tubular piston rod 53.

A cylinder 51 is reciprocable on the piston 54. The lower end of the cylinder 5'! is secured to a transverse lift bar 58 whose outer ends are secured to the lower end of the intermediate member 4|. The upper end of the cylinder 5'! is closed by cylinder head means 59 extending across the bore of the cylinder 51.

The bridge member 5| has formed therein a duct 66 which communicates at its inner end with the lower end of the bore 56 of the piston rod 53.

One end of the bridge duct 63 communicatingly connects with one end of a fluid supply tube 6|. Check valve means (not shown) are interposed between the fluid supply tube 6| and the bridge duct 63.

The bridge member 5| also has formed therein another duct 52 which also communicates at its inner end with the lower end of the bore 56 of the piston rod 53, and the duct 62 communicates at its outer end with fluid discharge valve means indicated generally by 63.

An upwardly opening sump pan 55' is secured within the base member bottom ring 24, the bottom of the sump pan being below the bridge member 5| and the fluid discharge valve means 63, and the side walls of the sump pan 65 extending about the same for receiving fluid discharged from the valve means 63 and otherwise as by operation of the present improvements, as hereinafter described.

The inlet 55 of the rotary fluid pump 33 communicatingly connects with the upper end of a fluid intake tube 31, the lower end of which depends into and terminates just above the bottom of the sump pan 55.

A supply of working fluid, the upper level of which is indicated by the horizontal dash line 58 in Fig. 3, is contained in the sump pan 65. When the rotary fluid pump 33 is operated by the electric drive motor l5, the Working fluid, usually oil, is pumped from the sump pan 65, through the pump 33, the fluid supply tube 6|, the duct 53, the piston bore 56, and into the cylinder chamber 69 formed by and between the piston 54 and the cylinder 51 and cylinder head means 59, lifting the cylinder 51 and the intermediate telescoping member 41 secured thereto. The lift of the telescoping member 4| causes a lift of the supporting member l3 through the action. of the chain lift means 46.

During the lifting operation of the members 4| and I3, the discharge valve means 63 is closed.

For the purposes of the present improvements, at the lower end of the cylinder 5? there is formed in its side walls one or more relatively small metering orifices T0.

The metering orifice or orifices iii are spaced from the cylinder head 59 a distancce equal to the desired maximum upward displacement or movement of the cylinder 51 and cylinder head 58 on the piston 54, which has a fluid sealing slidable fit in the bore of the cylinder 5'! as by usual packing washer means. When the cylinder 51 has moved upwardly to the position of maximum upward displacement shown in Fig. 3, the metering orifices F8 are just above the top of the piston 54, and the working fluid being pumped from the tubular piston 55 through the opening 55 into the cylinder chamber 69 is by-passed through the metering orifices 15 at a rate which is just suflicient to maintain the cylinder 5'! in its upper position with the metering orifices 10 above the piston 54, the pressure in the working fluid in the cylinder chamber 69 being maintained sufficiently for this purpose, without building up undesirable back pressure in the cylinder chamber 69.

The metering orifices 10 thus function as com-- bined stop means limiting the upward movement of the cylinder 51 and pressure relief means limiting the maximum pressure in the working fluid in the cylinder chamber 69 to that sufficient to maintain the cylinder 51 in its upper position While the motor pump unit 32 is operated.

' The motor |5 of the motor pump unit 32 is started and stopped by depression of either of the pedal levers 35 or 35, each of which is secured to the shaft 34 which also has secured thereon in a usual manner a mercury tilt switch, not shown, which closes the power circuit into the motor when either of the pedal levers 36 or 38 is depressed.

When the motor is stopped by release of foot pressure from either of the pedal levers 35 or 38, the shaft 34 rotates upwardly under spring pressure in a usual manner opening the. motor power circuit, and the cylinder 51 then drops slightly until the metering orifices pass below the top of the piston 54.

The discharge valve 63 is of usual construction and'is normally maintained by spring pressure in closed position. Depression of the middle pedal lever 37 serves to open the discharge valve means 53 permitting flow of the working fluid from the cylinder chamber 69 through the tubular piston rod 55, the ducts 62, and the valve means 53 into the sump pan 65.

The total area of the me tering orifice or orifices ll! is determined for each particular diameter of the cylinder 51 and maximum desired pressure in the working fluid in the cylinder chamber 69 to permit the above indicated by-pass flow of the working fluid through the metering orifice iii.

For preventing undesired noises caused by the by-passing of the working fluid through the metering orifices ll], external bafile means are mounted on the cylinder as shown in the form of a sleeve ll which engirdles the cylinder 57, and whose inner surface is spaced from the outer surface of the cylinder 51, the sleeve H covering or being opposed to the side opening metering orifices Ill, the upper end of the sleeve being open and spaced from the outer surface of the cylinder 5?. When the working fluid is being by-passed from the metering orifices 'iil the streams from the metering orifice strike the opposed sleeve inner surface and fill up the annular space having an open upper end between the sleeve i i and the cylinder 51, the lower end of the sleeve ll being seal connected on the cylinder 5'? a substantial distance below the metering orifices l0, and the top of the sleeve being located a substantial distance above the metering orifice 78. When this annular space or compartment is filled, the by-passed working fiuid spills over the top of the sleeve H into the sump pan B5.

The embodiments of the present improvements illustrated and described herein are by way of example, and the scope of the present invention is not limited to the same or to the particular details thereof, but is commensurate with any and all novel subject matter contained herein which may at any time properly under the patent laws be forth in the claims hereof or originating herein, the elements of any of which claims are intended. to include their reasonable mechanical and functional equivalents.

I claim:

1. In a fluid operated jack apparatus, cylinder chamber forming members including a piston, a cylinder having a fiuid sealing sliding fit on the piston and the piston and cylinder being relatively reciprocable with respect to each other, the cylinder having a bore and having a cylinder head extending" across the bore opposite the piston, and the cylinder chamber being formed by and between the piston and the cylinder and the cylinder head, one of the cylinder chamber forming members having a fluid inlet opening formed therein, and the cylinder having formed therein a side opening metering orifice, the metering orifice being spaced from the cylinder head in the direction of relative movement of the piston and cylinder a distance determining the maximum extension of the piston and cylinder with respect to each other; and external bafile means on the cylinder opposite the metering orifice, the external baffle means including walls forming a, compartment opposite the metering orifice and the compartment having a closed lower end below the orifice and an open upper end above the orifice.

2. In a fluid operated jack apparatus, cylinder r .chamber forming members including a piston, a

cylinder having a fluid sealing sliding fit on the piston and the piston and cylinder being relatively reciprocable with respect to each other, the cylinder having a bore and having a cylinder head extending across the bore opposite the piston, and the cylinder chamber being formed by and etween the piston and the cylinder and the cylinder head, one of the cylinder chamber forming members having a fluid inlet opening formed therein, and the cylinder having formed therein a side opening metering orifice, the metering orifice being spaced from the cylinder head in the direction of relative movement of the piston and cylinder a distance determining the maximum extension of the piston and cylinder with respect to each other, and an external cylindric bafiie sleeve engirdling the cylinder, the inner surface of the bafile sleeve being spaced from the outer surface of the cylinder and having a portion opposite the metering orifice and the lower end of the bafiie sleeve having a sealed connection with the cylinder below the metering orifice and the upper end of the sleeve being open and spaced from the cylinder.

3. In a fluid operated jack apparatus, a base, a tubular piston rod extending upwardly from the base, an annular piston on the piston rod above the base, a cylinder having a fluid sealing sliding t on the piston and movable up and down on the piston, the cylinder having a bore and having a cylinder head extending across the bore opposite the piston, and a cylinder chamber being formed by and between the piston and the cylinder and the cylinder head, and the upper end of the tubular piston rod opening into the cylinder chamber, and the cylinder having formed therein a side opening metering orifice, the metering orifice being spaced from the cylinder head in the direction of up and down movement of the cylinder on the piston a distance determining the maximum upward movement of the piston, and external baille means on the cylinder opposite the metering orifice, the external baflle means including walls forming a compartment opposite the metering orifice and the compartment having a closed lower end below the orifice and an open upper end above-the orifice.

4. In a, fiuid operated jack apparatus, a base, a tubular piston rod extending-upwardly from the base, an annular piston on the piston rod above the base, a cylinder having a. fluid sealing sliding fit on the piston and movable up and down on the piston, the cylinder having a bore and having a cylinder head extending across the bore opposite the piston, and a cylinder chamber being formed by and between the piston and the cylinder and the cylinder head, and the upper end of the tubular piston rod opening into the cylinder chamber, and the cylinder having formed therein a side opening metering orifice, the metering orifice being spaced from the cylinder head in the direction of up and down movement of the cylinder on the piston a distance determining the maximum upward movement of the piston, and an external cylindric baiile sleeve engirdling the cylinder, the inner surface of the baiile sleeve being spaced from the outer surface of the cylinder and having a portion opposite the metering orifice and the lower end of the baille sleeve having a sealed connection with the cylinder below the metering orifice and theupper end of the sleeve being open and spaced from the cylinder.

5. In a fluid operated jack apparatus, cylinder chamber forming members including a piston, a cylinder having a fluid sealing Sliding fit on the piston and the piston and cylinder being relatively reciprocable with respect to each other, the cylinder having a bore and having a cylinder head extending across the bore opposite the piston. and the cylinder chamber being formed by and between the piston and the cylinder and cylinder head, one of the cylinder chamber forming members having a fiuid inlet opening formed therein, and the cylinder having formed therein a side opening metering orifice, the metering orifice being spaced from the cylinder head in the direction of relative movement of the piston and cylinder a distance determining the maximum extension of the piston and cylinder with respect to each other, and an external cylindric bafile sleeve engirdling the cylinder, the inner surface of the bailie sleeve being spaced from the outer surface of the cylinder and having a portion opposite the metering orifice, and the bafile sleeve having a lower end seal connected on the cylinder a substantial distance below the metering orifice, and the bafiie sleeve having an open upper end spaced from the cylinder and located a substantial distance above the metering orifice.

6. In a fluid operated jack apparatus, a base, a tubular piston rod extending upwardly from the base, an annular piston on the piston rod above the base, a cylinder having a fluid sealing sliding fit on the piston and movable up and down on the piston, the cylinder having a bore and having a cylinder head extending across the bore opposite the piston, and a cylinder chamber being formed by and between the piston and the cylinder and the cylinder head, the upper end of the tubular piston rod opening into the cylinder chamber, and the cylinder having formed therein a side opening metering orifice, the metering orifice being spaced in the cylinder head in the direction of up and down movement of the cylinder on the piston a distance determining the maximum upward movement of the piston, and an external cylindric baflle sleeve engirdling the cylinder, the inner surface of the baflle sleeve being spaced from the outer surface of the cylinder and having a portion opposite the metering orifice, and the bafile sleeve havin a lower end seal connected on the cylinder a substantial distance below the metering orifice, and the baffie sleeve having an open upper end spaced from the cylinder and located a substantial distance above the metering orifice.

HAROLD E. NELIUS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 201,114 Lewis Mar. 12, 1878 762,086 Ritter June '7, 1904 1,069,863 Despins Aug. 12, 1913 1,233,859 Fertig et a1. July 17, 1917 1,271.978 Wood July 9, 1918 1,455,224 Paoli May 15, 1923 2,166,218 Morrison July 18, 1939 FOREIGN PATENTS Number Country Date 441,361 France May 23, 1912 

